More Computer Problems.

[Ruthenium]

Alright, some of you may remember that little problem with me and replacing a computer's hard drive. I've got another problem to solve before I let MicroCenter hold it hostage.
For some reason, that computer will not power up any more. I've tested the PSU, and all of the voltages seem fine. I've replaced it anyways, and it didn't solve the problem. The lights on the motherboard/LAN card light up, which tells me that it is getting power, but something's preventing it from starting up. I have tried WOL, but it didn't work for me, since it probably wasn't enabled.
Could it be a problem with the Power button? What do you guys think, because I'd rather not lug the heavy machine over to an electronics store.

[nensondubois]

It's entirely possible. I don't know much about replacing power buttons. I can replace power supplies, hard drives and lots of other stuff but I'm still one of the tech guys here. I can fix pretty much anything else including game systems and what-not.

[133MHz]

As a PC repair guy, one of the techniques you learn and use to bench test motherboards without a tower case is placing the motherboard on a clear, non conductive surface, connect the PSU, keyboard and video cables and then short the power switch contacts on the case LEDs & buttons connector block with the tip of a screwdriver in order to "jump start" the system. If you don't know which contacts correspond to the power on signal, slide the screwdriver across all of the contacts on the jumper block until the board springs to life. No harm done if you're careful.

By your description I assume your motherboard is completely dead except from the standby lights (the power LED doesn't come on, the CPU fan never starts spinning). As you said the power button itself could be flaky, and the best way to test it is by bypassing it completely and shorting the contacts together directly on the motherboard. If the system starts up successfully, replace the power button.

On the other hand if it still doesn't power up, the most probable cause is a short circuit somewhere. The mobo could be shorting out to the metal casing due to connector stress, loose or incorrectly installed screw standoffs or by sheer bad luck. Remove the mobo from the casing and use the bench test method to discard that possibility. The short could also be lying inside the PCI or memory slots (tiny specks of dust can be conductive and cause trouble). Use compressed air to blow the dust off every slot and component.

If you mobo still won't power up, you'll have to start swapping out components like the CPU or RAM until you pinpoint the cause.

If your mobo powers up but it doesn't POST, then we're on a whole different league of problems.